Wi-Fi Direct vs. Bluetooth 4.0: A Battle for Supremacy

The fight is on for wireless device-to-device networking supremacy between a refreshed incumbent, Bluetooth 4.0, and a newcomer, Wi-Fi Direct. Both specifications are promising to make it easier for you to quickly transfer pictures, files and other data between two wireless devices such as your smartphone and laptop without the need for a Wi-Fi network or USB cable.

Meanwhile, the Bluetooth Special Interest Group announced in July that it would soon start certifying Bluetooth 4.0 devices. Just like Wi-Fi Direct, Bluetooth 4.0 is promising speedy device-to-device transfers over long distances, and Bluetooth 4.0 devices should also hit the market in the coming months.

Can Wi-Fi Direct and Bluetooth 4.0 complement each other or will one crush the other in a wireless specification battle for the ages? Only time will tell. Until then, here's a quick look at the major highlights of Bluetooth 4.0 and Wi-Fi Direct.

Wi-Fi Direct? I thought Wi-Fi devices already had an ad hoc mode.

In Wi-Fi Alliance terms, ad hoc refers to an aging Wi-Fi device-to-device transfer method that was painful to set up and maxed out at data transfer speeds around 11 Mbps. Wi-Fi Direct, on the other hand, promises regular Wi-Fi speeds of up to 250 Mbps. Wi-Fi Direct also promises to be much easier to set up and use than ad hoc.

What's up with Bluetooth 4.0. Didn't we just get Bluetooth 3.0?

Bluetooth 4.0 is an upgrade from Bluetooth 3.0 that includes a power-saving feature called "low-energy technology." Basically, Bluetooth 4.0 is three Bluetooth specs in one. Bluetooth 4.0 not only uses the new low-energy technology, but also relies on high-speed data transfers introduced in Bluetooth 3.0 and so-called classic Bluetooth technology found in older Bluetooth specifications. The tricky thing is that Bluetooth 4.0's low-energy technology is not compatible with existing Bluetooth devices. However, that doesn't mean your new Bluetooth 4.0-equipped smartphone wouldn't be able to work with a Bluetooth 2.1 headset.

It means that a device that only uses Bluetooth's low-energy technology wouldn't be able to talk to an older Bluetooth device. Let's say you have a Bluetooth pedometer that only has Bluetooth 4.0's low-energy feature baked in (and not the other parts of the Bluetooth 4.0 spec). You wouldn't be able to transfer via Bluetooth the pedometer's data to an older laptop equipped with Bluetooth 2.1.

It should be pointed out, however, that manufacturers could incorporate low-energy technology into a newer device using Bluetooth 2.1 or Bluetooth 3.0. So the backward compatibility problem only affects older Bluetooth devices, and not the actual Bluetooth specifications.

Bluetooth 4.0 vs. Wi-Fi Direct: Speed

Wi-Fi Direct promises device-to-device transfer speeds of up to 250Mbps, while Bluetooth 4.0 promises speeds similar to Bluetooth 3.0 of up to 25Mbps. Both Bluetooth 4.0 and Wi-Fi Direct use the 802.11 networking standard to reach their maximum speeds. But whether Bluetooth or Wi-Fi Direct speeds will run as fast as promised in the real world remains to be seen. In other words, don't believe the hype and keep an eye on independent data speed tests to see how each specification performs.

How far can these specs travel?

The Wi-Fi Alliance is claiming that Wi-Fi Direct devices can reach each other at a maximum distance of 656 feet (more than two football fields) away. Why you would ever need that kind of distance between two devices is beyond me. Sufficed to say, it shouldn't be a problem for the laptop in your bedroom to communicate with the printer in your den via Wi-Fi Direct.

The Bluetooth SIG says that Bluetooth 4.0's maximum range is not dependent on the specification, but on the capabilities of the Bluetooth device. That said the Bluetooth SIG suggests a distance of at least 200 feet for a Bluetooth 4.0 device.

Security

Bluetooth 4.0 is using AES 128-bit encryption, while Wi-Fi Direct relies on WPA2 security, which uses AES 256-bit encryption. Both forms use key-based encryption and authentication methods, and both offer enough security for the average consumer.

Who's got the power?

Both the Bluetooth SIG and the Wi-Fi Alliance are claiming their specifications will use power-saving technology for battery-powered devices. The Bluetooth SIG says the new low-energy technology (PDF) feature means that Bluetooth 4.0 chips are optimized to run on a coin cell battery for a year or longer. But low-energy technology is only meant to be used when transferring short bursts of data. It also won't work if you are trying to talk to an older Bluetooth device that lacks the low-energy feature. That means laptops and mobile phones with Bluetooth 4.0 will have to switch between the new low-energy technology and so-called classic Bluetooth technology depending on the device they are talking to and how much data they are transferring. The bottom line is that while Bluetooth 4.0's power-saving feature sounds impressive, it's not clear how often you will get to take advantage of it in the real world.

The Wi-Fi Alliance says Wi-Fi Direct devices can support the WMM Power Save program that promises to improve a device's battery life by 15 to 40 percent.

Backward compatibility?

Wi-Fi Direct devices will be able to communicate with legacy Wi-Fi devices. That means if your next laptop has a Wi-Fi Direct chip, you will be able to create a device-to-device connection with your old wireless printer or wireless digital picture frame.

As I've already said, Bluetooth 4.0's new low-energy technology means that compatibility with older Bluetooth devices could get a bit messy. Some Bluetooth 4.0 devices such as pedometers and glucose monitors will only come with Bluetooth's low-energy feature using a single-mode Bluetooth radio. Since these single-function devices are meant to be small and mobile, they use the new power-saving feature to save space and battery power. But that means they are also incompatible with, say, an older PC equipped with Bluetooth 2.1.

More complex devices using Bluetooth 4.0, such as PCs and mobile phones, will use a dual-mode radio to take advantage of all three Bluetooth 4.0 technologies - low-energy, high-speed transfers and classic Bluetooth. This will make it possible for newer Bluetooth 4.0 devices to communicate with legacy Bluetooth tech.

It's also important to note that so-called "streaming devices" such as hands-free headsets for mobile phones or stereo equipment cannot use Bluetooth low energy technology. That means new Bluetooth headsets for your iPhone 4, Droid X or Samsung Focus should not be affected by Bluetooth 4.0's use new low-energy technology. For more information, check out the Bluetooth SIG's FAQ about low energy technology (PDF).

Availability

Bluetooth 4.0 products should start hitting the market before the end of the year or early 2011. But it looks like Wi-Fi Direct may be first out the gate. The Wi-Fi Alliance recently announced that five wireless networking PC cards from Atheros, Broadcom, Intel, Ralink and Realtek are Wi-Fi Direct ready and should be available before the end of the year.

The screen was particularly good. It is bright and visible from most angles, however heat is an issue, particularly around the Windows button on the front, and on the back where the battery housing is located.

My first impression after unboxing the Q702 is that it is a nice looking unit. Styling is somewhat minimalist but very effective. The tablet part, once detached, has a nice weight, and no buttons or switches are located in awkward or intrusive positions.

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